Most NBA coaches shorten their bench during the playoffs and go with their best 8 or 9 players. I am not sold on any particular reason for doing this as I would rather go with the best match ups and with players who seem to "have it" on certain nights rather than be committed to a short rotation where certain players might struggle.
The line up changes that I would prefer to see would be to limit Billups to backing up CP3 at the point, starting Bledsoe at the two-guard, and favoring Hill over Barnes in the rotation at the wing. Barnes would play much fewer minutes because I think Hill is still the better overall defender than Barnes.